Method and system for invasive skin treatment

ABSTRACT

A system and method for simultaneously heating a plurality of discrete skin volumes to a coagulation temperature. The system comprises an applicator containing an electrode having a plurality of spaced apart protruding conducting elements configured to contact the skin surface at a plurality of discrete locations. A controller applies a voltage to the electrode so as to simultaneously heat a plurality of skin volumes to a coagulation temperature when the applicator is applied to the skin surface.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is being filed under 35 USC 111 and is a continuation of, and claims the benefit of the filing date of U.S. patent application Ser. No. 12/702,723 and U.S. patent application Ser. No. 12/702,647, both of which were filed on Feb. 9, 2010 and both of which claim priority to U.S. patent application Ser. No. 10/931,271 that was filed on Sep. 1, 2004 and bears the title of METHOD AND SYSTEM FOR INVASIVE SKIN TREATMENT and which has now been abandoned.

FIELD OF THE INVENTION

The invention relates to methods and systems for skin treatment.

BACKGROUND OF THE INVENTION

Directed damage of the skin is used to stimulate regrowth of collagen and to improve skin appearance. A well known method of directed damage is ablating the epidermis using laser radiation having wavelengths strongly absorbed by water so as to heat the water to above boiling temperature. Typical lasers used for epidermis ablation are CO.sub.2 and Er:YAG lasers. Ablating the epidermis using RF (radiofrequency) current is described in U.S. Pat. No. 6,309,387. This treatment significantly reduces wrinkles and improves the skin appearance. The main disadvantages of skin resurfacing are the long healing period that can be over a month long and the high risk of dischromia. These disadvantages have reduced the popularity of ablative skin resurfacing in recent years.

Non-ablative skin resurfacing is based on heating of the dermis to a sub-necrotic temperature with simultaneous cooling of the skin surface. U.S. Pat. No. 5,810,801 describes penetrating the dermis with infrared laser radiation with dynamic cooling of the skin surface using a cryogen spray.

Wrinkles are created in skin due to the breakage of collagen fibers and to the penetration of fat into the dermal structure. Thus, destroying adipose cells and structure, can improve the surface structure. However, most wrinkle treatment methods target the collagen and do not have a significant effect on deep wrinkles. Radio frequency (RF) energy has been used for the treatment of the epidermal and dermal layers of the skin. For example, U.S. Pat. No. 6,749,626 describes use of RF for collagen formation in dermis. This patent describes a method for collagen scar formation. U.S. Pat. Nos. 6,470,216, 6,438,424, 6,430,446, and 6,461,378 disclose methods and apparatuses for affecting the collagen matrix using RF with special electrode structures together with cooling and smoothing of the skin surface. U.S. Pat. Nos. 6,453,202, 6,405,090, 6,381,497, 6,311,090, 5,871,524, and 6,452,912 describe methods and apparatuses for delivering RF energy to the skin using a membrane structure. U.S. Pat. Nos. 6,453,202 and 6,425,912 describe methods and apparatuses for delivering RF energy and creating a reverse temperature gradient on the skin surface. Although a non-ablative treatment is much safer and does not scar the skin tissue, the results of non-ablative treatments are less satisfactory.

A method described in U.S. patent application No. 20030216719 attempts to maintain the efficiency of ablative treatment with a shorter healing time and a lower risk of adverse effects. The device described in that patent coagulates discrete regions of the skin where the regions have a diameter of tens of micrometers and the distance between the regions is larger than the regions themselves. This treatment provides skin healing within a few days but the results are very superficial and less spectacular than with CO.sub.2 laser treatment, even after multiple treatments.

U.S. Pat. No. 6,277,116 describes a method of applying electromagnetic energy to the skin through an array of electrodes and delivery electrolyte using a microporous pad.

A device for ablation of the skin stratum corneum using RF electrodes is described in U.S. Pat. Nos. 6,711,435, 6,708,060, 6,611,706, and 6,597,946. However, the parameters of this device are optimized for the ablation of the stratum corneum so as to enhance drug penetration into the skin, and not for thermal collagen remodeling.

SUMMARY OF THE INVENTION

The present invention provides a system and method for simultaneously heating skin at a plurality of discrete regions of the skin. The invention may be used for collagen remodeling. In accordance with the invention RF energy is applied to the skin at a plurality of discrete locations on the skin. The RF energy is applied using an electrode having a plurality of spaced apart protruding conducting pins. When the electrode is applied to the skin surface, each protruding conducting pin contacts the skin surface at a different location, so that the plurality of pins contacts the skin at a plurality of discrete locations. An RF voltage is then applied to the electrode so as to generate an electric current in the skin that heats the skin to a coagulation temperature simultaneously at a plurality of discrete regions of the skin. Coagulation temperatures are typically in the range of about 60.degree. C. to about 70.degree. C.

The protruding pins may have blunt tips which do not penetrate into the skin when the electrode is applied to the skin. In this case, the discrete regions of treated skin are located at the skin surface in the epidermis. Alternatively, the pins may have sharp tips that allow the protruding pin to penetrate the skin into the dermis. In this way, the discrete regions of treated skin are located in the dermis.

In another embodiment, the protruding elements are provided with sharp tips that allow the elements to penetrate into the skin. After application of the RF current in the skin, the protruding elements are pressed into the skin and an electrical current is then generated that coagulates tissue in the vicinity of the tip of each protruding element. The mechanical properties of the skin are changed after coagulation and the protruding elements may penetrate inside the skin without excessive pressure. A pre-pulse of RF energy can be applied to the skin in order to soften the skin tissue so as to facilitate penetration of the protruding elements into the skin.

The surface of the skin may be pre-cooled and/or cooled during the treatment to avoid damage to the skin in the area between protruding elements. Skin cooling may be provided by contact cooling or by applying a pre-cooled liquid or cryogen spray.

The invention may be used in wrinkle treatment, collagen remodeling, skin tightening, loose skin treatment, sub-cutaneous fat treatment or skin resurfacing.

Thus in its first aspect, the invention provides a system for simultaneously heating a plurality of discrete skin volumes to a coagulation temperature, comprising:

-   -   (a) an applicator comprising an electrode having a plurality of         spaced apart protruding conducting elements configured to         contact the skin surface at a plurality of discrete locations;         and     -   (b) a controller configured to apply a voltage to the electrode         so as to simultaneously heat a plurality of skin volumes to a         coagulation temperature when the applicator is applied to the         skin surface.

In its second aspect, the invention provides a method for simultaneously heating a plurality of discrete skin volumes to a coagulation temperature, comprising:

-   -   (a) applying an applicator to the skin surface, the applicator         comprising an electrode having a plurality of spaced apart         protruding conducting elements configured to contact the skin         surface at a plurality of discrete locations; and     -   (b) applying a voltage to the electrode so as to simultaneously         heat a plurality of skin volumes to a coagulation temperature.

In the case when protruding part of the electrode penetrates within the skin the size of protruding elements should be small enough to avoid significant damage of the skin surface. Preferable size of protruding elements is from 10 to 200 microns and coagulation depth can be varied from 100 microns up to 2 mm for invasive electrodes.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to understand the invention and to see how it may be carried out in practice, preferred embodiments will now be described, by way of non-limiting examples only, with reference to the accompanying drawings, in which:

FIG. 1 shows a system for treating skin simultaneously at a plurality of discrete regions of skin, in accordance with the invention;

FIG. 2 shows an applicator for use in the system of FIG. 1;

FIG. 3 shows a second applicator for use in the system of FIG. 1; and

FIG. 4 shows a third applicator for use in the system of FIG. 1.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 shows a system for applying RF energy to a plurality of discrete regions of skin in accordance with the invention. The system includes an applicator 13, to be described in detail below, configured to apply RF energy simultaneously to a plurality of discrete regions of skin of an individual 22. The applicator 13 is connected to a control unit 11 via a cable 12. The control unit 11 includes a power source 18. The power source 18 is connected to an RF generator 15 that is connected to electrodes in the applicator 13 via wires in the cable 12. The control unit 11 has an input device such as a keypad 10 that allows an operator to input selected values of parameters of the treatment, such as the frequency, pulse duration and intensity of the RF energy. The control unit 11 optionally contains a processor 9 for monitoring and controlling various functions of the device.

FIG. 2 shows an applicator 13a that may be used for the applicator 13 in accordance with one embodiment of the invention. The applicator 13 a comprises an electrode 1 from which a plurality of protruding conducting elements 5 extend. Each protruding element 5 (referred to herein as a “pin”) terminates in a tip 7 having a high curvature. The electrical current from the tips is much higher than from flat parts 6 of the electrode. Skin volumes 4 around the tips 7 are therefore heated to a much higher temperature than the surrounding dermis 3 and epidermis 2, so that the skin volumes 4 may be heated to a coagulation temperature, while the skin temperature in the outside the volumes 4 are not heated to a coagulation temperature. The electrical energy is adjusted to selectively damage skin adjacent to tips so that the treatment of the skin occurs simultaneously at a plurality of discrete volumes 4. The pulse duration is preferably short enough to prevent significant heat diffusion far from the tips. In order to limit significant heat transfer from the tips, the pulse duration should preferably not exceed 200 ms. The selectivity of the treatment can be improved by electrode cooling of the skin surface. Cooling also causes a more uniform heat distribution at the tips. This can be achieved by circulating a cooling fluid through tubes 8 in the flat regions 6 between the pins 5. The electrode 1 is contained in a housing 10 connected to the cable 12. The cable 12 electrically connects the electrode 1 with a terminal of the power source 18. A second terminal of the power supply 18 may be connected to a ground electrode 20 via a cable 23 (See FIG. 1).

FIG. 3 shows an applicator 13 b that may be used for the applicator 13 in accordance with another embodiment of the invention. The applicator 13 b comprises an electrode 100 consisting of a plurality of conducting pins 101 extending from a conducting plate 102. The pins 101 are separated by electrical insulating material 105. The applicator 13 b is used similarly as the applicator 13 a to deliver electrical current to discrete volumes of skin 4.

The pins 5 in the applicator 13 a and the pins 101 in the applicator 13 b are provided with blunt tips 7 and 107, respectively. This prevents the pins 5 and 101 from penetrating into the skin when the electrode 13 a or 13 b is applied t the skin surface. Thus, the applicators 13 a and 13 b provide simultaneous non-invasive coagulation of skin regions 4.

FIG. 4 shows an applicator 13 c that may be used for the applicator 13 in accordance with another embodiment of the invention. The applicator 13 c is configured to be used for invasive collagen remodeling. The applicator 13 c includes an electrode 201 having a plurality of protruding conducting pins 205. The pins 205 have sharp tips 206 that are configured to penetrate through the epidermis 202 into the dermis 203 when pressed on the skin as shown in FIG. 4. The applicator 13 c is used similarly to the applicators 13 a and 13 b so that the treatment of the skin occurs simultaneously in a plurality of discrete skin volumes 204. However, unlike the discrete volumes 4, which are located in the epidermis (see FIGS. 2 and 3), the volumes 204 are located below the surface in the dermis 203 (FIG. 4). This reduces skin redness that sometimes occurs when the treated regions are in the epidermis. A maximal current density is created at the tips of the pins 205. The sides of the protruding elements may be coated with insulating material to avoid skin heating around the pins 205 (not shown).

The present invention can be combined with other methods of skin treatment including laser treatment. For example non-ablative collagen remodeling by laser radiation may be combined with the invasive RF heating of the skin dermis in accordance with the invention.

The preferable parameters for non-invasive skin coagulation in accordance with the invention are as follows: Electrode size above 0.3 cm; Protruding element at contact with the skin up to 0.5 mm Protruding element height about 1 mm. Distance between protruding elements at least twice the element diameter; Current density: over 1 A/cm.sup.2; RF current pulse duration: not longer than 0.5 sec; The optimal parameters for invasive skin coagulation: Electrode size above 0.3 cm; Pin diameter at contact with the skin not larger than 0.3 mm Pin protruding height above 1 mm. Distance between pins at least 1 mm; Current density above 0.1 A/cm.sup.2; RF current pulse duration not longer than 0.5 sec. 

1. A method for heating one or more discrete skin volumes to a target temperature, the method comprising the acts of: placing an applicator to a surface region of the skin, wherein the applicator is configured to deliver radio frequency (RF) energy and is comprised of at least one electrode having at least one protruding conducting element configured to contact the surface region of the skin via a distal tip element; and supplying a voltage to a control unit that generates the RF energy that is delivered to the distal tip element of the at least one protruding conducting element; wherein the supplied RF energy serves to heat a volume of skin proximate to the surface region contact point of the distal tip element.
 2. The method of claim 1, wherein the target temperature is sufficient to result in coagulation and the act of supplying a voltage to the applicator further results in supplying an RF energy that is sufficient to cause the volume of skin being heated to the coagulation temperature.
 3. The method of claim 1, further comprising the act of selecting an intensity of the RF energy for supply to the applicator.
 4. The method of claim 1, further comprising the act of selecting the frequency of the RF energy.
 5. The method of claim 1, further comprising the act of selecting the pulse duration of the RF energy.
 6. The method of claim 1, further comprising the step of cooling areas within the surface region of the skin.
 7. The method of claim 6, wherein the applicator electrode further comprises one or more cooling elements and the areas within the surface region of the skin are cooled via contact with the applicator electrode.
 8. A method for heating one or more discrete skin volumes to a target temperature, the method comprising the acts of: placing an applicator to a surface region of the skin, wherein the applicator is operable to deliver radio frequency (RF) energy and is comprised of at least one electrode having at least one protruding conducting element configured to contact the surface region of the skin via a distal tip element; providing a pulse of RF energy to the applicator such that the RF energy is delivered to the distal tip element of the at least one protruding conducting element; applying a force to the applicator such that the distal tip element of the at least one protruding conducting element penetrates the skin into the dermis; and wherein the provided pulse of RF energy serves to soften an area of skin around the surface region contact point of the distal tip element; and wherein the supplied RF energy serves to heat a volume of skin tissue surrounding the positioned distal tip element to the target temperature.
 9. The method of claim 8, wherein the target temperature is sufficient to result in coagulation and the act of providing a pulse of RF energy to the volume of skin results in heating the volume of skin to the coagulation temperature.
 10. The method of claim 8, further comprising the act of selecting an RF energy intensity level to be provided to the applicator.
 11. The method of claim 8, further comprising the act of selecting the frequency of the RF energy.
 12. The method of claim 8, further comprising the act of selecting the pulse rate of the provided pulse of RF energy.
 13. The method of claim 8, further comprising the act of cooling areas within the surface region of epidermis.
 14. The method of claim 13, wherein the applicator electrode further comprises one or more cooling elements and the areas within the surface region of skin are cooled via contact with the applicator electrode.
 15. The method of claim 8, wherein the at least one protruding conducting element comprises an insulating material on its surface such that the only skin heated is proximate to the distal tip element.
 16. A method for simultaneously heating a plurality of discrete skin volumes to a coagulation temperature, the method comprising the acts of: (a) applying an applicator to the skin surface, the applicator comprising at least one electrode having a plurality of spaced apart protruding conducting elements configured to contact the skin surface at a plurality of discrete locations and, at least one of the conducting elements including a sharp tip on the end; (b) causing the at least one sharp tip on ends of the conducting elements to penetrate the epidermis of the skin when the applicator is applied to the skin; and (c) applying RF energy to the electrode so as to generate an electrical current in the skin simultaneously heating a plurality of skin volumes to a coagulation temperature.
 17. The method according to claim 16, further comprising the act of cooling the skin surface.
 18. The method according to claim 16, further comprising the act of providing the RF energy to the electrode in pulses.
 19. The method according to claim 18, wherein the pulses have a duration of less than 0.5 seconds.
 20. The method according to claim 20, further comprising the act of providing a prepulse of RF energy to the skin prior to the act of applying the applicator to the skin in such a way to penetrate into the dermis.
 21. A method for simultaneously heating a plurality of discrete skin volumes to a coagulation temperature, the method comprising the acts of: (a) applying an applicator to the skin surface, the applicator comprising at least one electrode having a plurality of spaced apart protruding conducting elements configured to contact the skin surface at a plurality of discrete locations and, the conducting elements include blunt tips on the end so that the skin surface is not penetrated; (b) applying RF energy to the electrode so as to generate an electrical current in the skin simultaneously heating a plurality of skin volumes to a coagulation temperature.
 22. The method according to claim 21, wherein the protruding elements have a diameter of 0.5 mm and the act of applying the applicator to the skin surface results in the protruding elements contact a 0.5 mm area of the skin surface.
 23. The method according to claim 21, wherein the protruding elements are spaced apart by a distance of at least 1 mm and the act of applying the applicator to the skin surface results in the protruding elements the skin surface at spaced apart discrete locations.
 24. The method according to claim 21, wherein the act of applying RF energy to the electrode further comprises applying RF energy sufficient to generate a current density of at least 1 Ampere/cm2 at the tips of the protruding elements.
 25. The method according to claim 21, further comprising the act of applying the applicator to cause collagen remodeling. 